Process and means for separating and purifying gas



arch 17, 1936. F GOODWlN ET AL 2,033,933 PROCESS AND MEANS FORSEPARATING AND PURIFYINGV GAS Filed April 2;I 1933 Patented Mar. 17,1936 UNITED STATES PROCESS AND MEANS Fon SEPARATING AND PURIFYING GASFrank Goodwin, Seattle, Wash., and E. Ambrose White and Hamilton PerkinsCady, Lawrence,

Kans.

Application April 21, 1

` 11 Claims. While the present invention relates to the separation andpurification of gases in general, it is more particularly applicable toseparation of carbon dioxide (CO2) gas from natural gases and 5 thepurification of the same.

Many natural. gas wells produce a mixed gas consisting mainly of a fuelgas admixed with carbon dioxide in varying proportions. Other wellsproduce a gas consisting almost entirelyA of carbon dioxide contaminatedwith other gases and compounds which render the carbon dioxide un-Vsuitable for commercial uses.

The principal object of this invention is to provide a process, andmeans for carrying out thev process, which will eiciently separate .thecarbon dioxide from the residual gases and efficiently purifyv thecarbon dioxide so that it will be acceptable for commercial uses.

Another object oi the present inventionris to,

provide a process for accomplishing the above and means and materialsfor carrying outV the process which will be economical to use; whichwill employ readily available raw materials; and which will obtain amaximum delivery from a minimum amount of material. v

A further object is to provide means for using water in the` separationphase ina more effective manner than it has been heretofore used in theart.

A still further object is to provide means for effectively using air inthe purication phase to activate and reactivate the purificationreagents so as to not only reduce thelcost of refining, but to alsoincrease the effectiveness and efficiency of the process.

Other objects and advantages reside in the process, the steps thereof,and in the materials and means employed. These will become more apparentfrom thefollowing description in which forming a part hereof.

In the drawing:

Fig. l is a flowdiagram.illustrating what will be herein designated the`separation phase of the. process.

Fig. 2 is a similar flow diagram illustrating what will beter-med theprocess;

Ifv the process is to be gas ci avery low purification phase. might notbe commercially advisable in which event the separatedcarbon dioxidewould be allowed to escape to the atmosphere and commercial use madeofthe residual fuel gas. If employed on a-natural gas of very high carbondioxide content the separation phase Awould be passed directly throughthefpurica- 60 tion phase. On natural gases having commerpurificationphase of the reference is had to the accompanying :drawing employed one.natural carbon dioxide content `the v could be eliminated and` the WellgasV 933, serial No. 667,166

(C1. ca -2) cially suiiicient amounts of both gases both phases l would,of course, be employed.

Separation phase The use of water for the separation of carbon 52 l1dioxide from other gases is of course not new. Heretofore, however, thegases have been bubbled through the water, sometimes with the employment of chemicals in the water intended to increase the absorptiveproperties of the solution. Such methods are not efficient unless aprohibitive volume or depth of Water is used. Ihis is due to the factthat an intimate contact cannot be obtained between the gas and thewater since the gas forms balloon-likebubbles, .only the gaseous surfaceof which contact the water. The midportions are entirely out of contact.

In the present process the Water is spread in an infinite number ofmicroscopic Yfilms on the surfaces ofthe granules of a granulated orcom- "minuted medium and the gas is compelled to passY through the voidsand interstices of a. mass of the Water coated granules in-intimatecontact with this multitude of water lms. Many mediums may be employedfor breaking up the water 25,

into, an infinite number of films. An ideal me-l dium for this purposehas been found to be activated alumina which has very high absorptivequalities and when moistened to the point of sat` uration, but notimmersed, produces a maximumV of absorptive contact. It is believed thesmallness of the pores and interstices of a mass of this materialtogether with its excellent absorptive qualities forms an infinitenumber of infinitely small water membranes of lms against which thehighlydispersed' gas must flow so that an intimate molecular contact isobtained.

The preferred method of carrying out the purication phase is Yto providea series of vertical towers I0 lled with granules ofthe water dis- 40persingcme 'um (such as the activated alumina). The towers `Ill areconnected in series by suitable series pipes I I. Gas from the well orother supply source is fed to the bottom of the `iirst tower'from a wellpipe I2 and discharges from 45 the last vtower through a fuel gas pipeI3. Wa- Y ter is supplied to a spray nozzle I4 in the top of each towerfrom a water main I5 and flows Y from the bottom of each tower throughreturn main I6.A The return main empties into a sepa-f 50 rating tank I1from whence a carbon dioxide delivery pipe I8 leads. The water from thetank I1 returns to a pump I9 which returns it to the sprays I4. l

The water from the sprays constantly washes the water, which hasabsorbed CO2 from the passing gas, from the dispersion medium to theseparating tank I1. While in the towers the water is subjected to therelatively high pressureof the gas therein. Whenit reaches thertank l1;thisBO. i

pressure is released to a point far below its initial pressure. Thiscauses the water to give up the major portion of its absorbed CO2 to thepipe I8. 'I'he returning water retains but a small percentage of thegas. Thus the CO2 gas is effectively and continuously separated from theresidual fuel gas iiowing through the fuel gas pipe I3.

Purification phase The separated CO2, or the natural CO2, if theseparation phase is not required, is not usually suitable for somecommercial purposes, such as for carbonating beverages or themanufacture of solid CO2 for use as a refrigerant, owing tocontaminating compounds which impart an unpleasant odor or taste andwhich, in some cases, are highly corrosive. The deleterious substancesusually comprise hydro-carbons and other carbon compounds, alcohols,sulfur, hydrogen-sulphide, mercaptans, thioethers and other sulfurcompounds.

It has been found that the above objectionable compounds can beeffectively and commercially removed by heating the gas and passing itwhile hot and under pressure through an oxidizing agent containingoccluded oxygen or air thence passing it through highly dispersed drysodium carbonate.

The oxidizing agent is preferably prepared of the following ingredientsin the following proportions:-

, Ounces Ferric oxide (Fe2O3) 27 Ferric chloride (FeCl3) 12 Activatedalumina Al2O3) 40 Aluminum chloride (A1Cl3) l2 'I'he ferric oxide ispreferably in powdered form like red mineral paint but may be crushedhematite ore. Aluminum in the form of bauxite may be substituted for theactivated alumina.

The above is mixed with water to the consistancy of a thick paste andthen dehydrated and Igranulated. The highly dispersed sodium carbonateis prepared by coating alumina granules with a thick sodium carbonatesolution and then -dehydrating to leave'each granule coated with .'drysodium carbonate. The granules are preferably alumina, crushed bauxite,or silica jell. The coating process is continued until all granules arecompletely coated with the maximum amount of solution which willmechanically adhere thereto.

The preferred method of carrying out the purification phase is.illustrated in Fig. 2 of the drawing. 'I'his method contemplates the useof a heater 20, of any desired type suitable for withstanding thenecessary pressures and of raising the CO2 gas to a temperature ofpreferably 450 F.; one or more oxidizing towers 2l one or more sodatowers 22,' one or more nal purification towers 23; a condenser 2Q; anda filter 25.

'Ihe oxidizing tower 2| is filled with the granun lated oxidizing agentabove described; the soda tower 22 is filled with the coated aluminagranules above described; and the final purification tower 23 ispreferably, but not necessarily, filled with the same oxidizing agent astower 2 I. The condenser 24 may be any suitable heat exchange unit. Thefilter` 25 is preferably of a type einploying spun glass or bulkasbestos as a lter medium.

The towers 2 I, 22 and 23 are connected in series by means of seriespipes pipes 26; the heater 2o is connected to the bottom of the ISttower 2! air receiver by a hot gas pipe 27; controlled by a valve 33;ycondensers 24 and 25 are connected in series to the top of the nal tower23 by means of a pure gas pipe 28 in which a control valve 34 and ablow-olf valve 29 are provided. A compressed 30 can be connected to thebottom of the first tower 2| through an air pipe 3| and air valve 32.The receiver 30 should be connected to a suitable source preferablycapable of supplying aproximately 400 lbs. pressure.

Before turning the gas into the apparatus, air is admitted to the towersthrough the pipe SI and Valve 32, the valves 33 and 34 being closed. Thehigh pressure of this air compresses it into all of the pores,interstices and voids of the granular, porous materials in the towers.The valve 32 is then closed leaving the tanks under air pressure. CO2gas is then turned into the heater 20 through a supply valve 34. Thisgas may come from any source. If from the separating phase it will haveto be run through suitable compressors to raise its pressure. Ifdirectly from the well, the natural pressure will ordinarily give it aninitial pressure of 600 lbs.

The high pressure at at least 200 and preferably 450 F., into the i'lrsttower 2l where it displaces the free air from the towers through theblow olf valve 29, the valve 313 being closed as yet. The valve 29 isclosed and the valve 34 is opened when the air has been displaced andgas begins to flow there-- from. The entrapped or occluded high pressureair is locked in the pores and interstices of the oxidizing agent by thestill higher pressure of the surrounding gas and and increase theoxidizing action of the oxidation medium per se. The principal oxidizingreactions between the various impurities and the retained air or oxygenare as follows.

(1) Hydrogen sulphide (HzS) 2H2S-I-O2=2H2O+2S or vunder the hightemperature and pressure present The heat and pressure also act toreduce the ferrie iron to the ferrous state and proportionately increaseits oxidizing action. The catalytic action of the chlorides assists theabove reactions by reacting with the hydrogen sulphide thus:-

From tower ZI the carbon dioxide gas, with the sulfur dioxide, moisture,hydrochloric and sulphurous acids etc. from the reactions in tower 2I,flows at reduced pressure and temperature into tower 22 where the acidsare neutralized by the sodium carbonate and the sulfur dioxide iseliminated by the following reactions:-

remains to assist in Bile The use of the coated granules in tower 22overcomes all of the disadvantages of employing soda in solution or as abody of dry soda. The

former is objectionable as it is prone to blow back into tower 2l duringstoppages and also because it produces a moisture laden gas which mustbe dehydrated before condensing. The use of a body of dry soda isobjectionable since caking from the gas moisture causes channel flowsand ineffectual contact.

The coated granules separate the gas into an innite number of innitelysmall streams each of which is brought into intimate and continuouscontact with the sodium carbonate.

The gas iiowing from tower 22 should be completely puried, however, thetower 23 is provided principally as a safety feature to remove anyremaining contamination which may have escaped removal in tower 2|.Tower 23 is preferably lled with the granular oxidizing agent of tower2|. It could, however, contain other reagents such as sodium carbonateand alum, coated as before on alumina, bauxite or silica jell granules,or it may contain any other absorbent such as charcoal, if desired.

From the final puriiication in tower 23 carbon dioxide flows throughpipe 28 to the condenser 24, thence through the filter to the finaldischarge valve 35. Because of its expansion in the towers 23 andcondensation in condenser 24 the carbon dioxide has been reduced to aliquid state by the time it reaches the lter 25. After filtering it isready for any desired commercial use. It may be stored in liquid bottlesfor beverage carbonation or expanded into snow crystals for themanufacture of solid carbon dioxide for refrigerating purposes.

The air can be renewed in the towers as often as necessary bymanipulation of the valves 32, 33, 29 and 34 so as tol maintain theoxidizing agent at its maximum efficiency. The reagent in tower 22 maybe reactivated by discharging the granules into an open pan in whichthey' may be heated and stirred to eliminate the impurities collected intower 22.

The number of towers employed is of course optional, depending upon thequantity of gas being treated and upon the degree of purity desired.

While preferred forms been described insome of the invention have detailtogether with the theories which it is believed to best explain itssuccess, it is to be understood that the invention is not limited to theprecise procedure Vdescribed nor is dependent upon the accuracy of thetheories which have been advanced. On the contrary, the invention is notto be regarded as limited except in so far as such limitations areincluded within the terms of the accompanying claims in which it is theintention to claim all novelty inherent in the invention as broadly as Yis permissible in view or" the prior art.

Having thus described the invention, what is claimed and desired securedby Letters Patent 1s:-

1. The process of removing oxidizable impurities from carbon dioxide gascomprising: subjecting said gas under the inuence of heat above thereaction temperature to the action of a porous oxidizing agent of a typeto convert the said impurities to an easily oxidizable state, the poresoi said oxidizing agent being iilled with air underipressure forcompleting the oxidation.

2. The process of removing oxidizable impurities from carbon dioxide gascomprising: heating said gas above the reaction temperature; thencepassing said hot gas through a dried mixture of ferrie oxide, ferricchloride and aluminum chloride in the presence of air.

3. The process of removing oxidizable impurities from carbon dioxide gascomprising: heating said gas; passing said hot gas in the presence ofair through a dried mixture of ferric oxide, ferric chloride, aluminumoxide, and aluminum chloride under the influence of sufficient heat andpressure to convert the ferrie iron to the ferrous state.

4. The process of removing oxidizable impurities from carbon dioxide gascomprising: heating said gas; thence passing said hot gas through adried mixture of ferrie oxide, ferrie chloride, activa-ted alumina andaluminum chloride in the presence of air. v

5. A medium for the puriiication of carbon dioxide comprising: a driedpaste of ferric oxide, ferric chloride, activated alumina and aluminumchloride.

6. A method of preparing a medium for the purification of carbon dioxidecomprising: forming a thick paste of ferrie oxide, ferrie chloride,activated alumina, and aluminum chloride; drying said paste; andgranulating the dried paste.

7. The process of purifying carbon dioxide gas comprising: heating saidgas to a temperature ranging from 200 to 450 F.; passing said heated gasunder a relatively high pressure through a porous oxidizing agentcontaining occluded air under pressure; thence passing said gas througha granular mass of inert granules, the surfaces of which are coated withsodium carbonate.

8. A medium for the purification of carbon dioxide comprising: a driedpaste of ferric oxide, ferrie chloride, bauxite, and aluminum chloride.

9. The process of removing oxidizable impurities from CO2 gascomprising: subjecting a porous oxidizing agent in a closed container toair under relatively high pressure; sealing said container so that thepressure of said air will be maintained in the pores .of said agentheating said CO2 gas to an oxidizable temperature; and thence forcingsaid heated CO2 gas at still higher pressure into said agent under theinfluence of heat.

10. The process of removing oxidizable impurities from CO2 gascomprising: passing air under pressure into a closed containercontaining a porous oxidizing agent; preventing escape of said air fromsaid container until a'relatively high pressure has been built up insaid agent; sealing said container to retain the pressure in said iagent; heating the CO2 gas to an oxidizable temperature; thence passingsaid heated gas into agent at a pressure greater than the pressure ofthe air sealed therein.

1l. The process of removing oxidizable impurities from CO2 gascomprising: passing air at approximately 400 lbs. per square inchpressure into a closed container containing a porous oxidizing agent;sealing said container so as to maintain approximately the full pressurein said agent; heating said CO2 gas to approximately 200 F. or more;thence passing said heated CO2 gas into said agent at a pressure greaterthan 400 lbs. per square inch so as to trap the lesser pressure air inthe pores of said agent.

FRANK GOODWIN. E. AMBROSE WHITE. HAMILTON PERKINS CADY.

